Multigrip fastener

ABSTRACT

A unique two-part fastener consisting of a pin and a tubular member adapted to be set by a tool having a set of jaws to grip the pin and a swaging anvil for swaging the collar onto the pin and in which the pin has a set of substantially identical annular grooves formed along a major portion thereof and in which the set of annular grooves provide combination grooves some of which function as locking grooves and a selected one which functions as a breakneck groove and in one form the fastener including a second set of grooves of a different construction which function only as pull grooves; the first set of grooves provide a unique relationship with a swaged portion of the tubular member so that as the fastener is set, the pin will break off in a preselected one of the combination grooves within the outer end of the tubular member; the second set of grooves provide a construction which is compatible with a known type jaw structure on the tool.

This is a continuation of application Ser. No. 26,652, filed Apr. 3,1979 and now abandoned, which is a continuation-in-part of U.S. patentapplication Ser. No. 899,591, filed Apr. 24, 1974, now U.S. Pat. No.4,208,943, issued June 24, 1980.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates generally to fasteners and morespecifically to two piece fasteners which are adapted to be utilized insecuring a broad range of material thicknesses.

In some applications it would be desirable to use a two piece fastenerof the type employing a pin having combination locking and breakneckgrooves and a tubular member adapted to be swaged thereto and in whichany of these grooves is capable of functioning as a breakneck so as toenable a single fastener to be utilized over a broad range of materialthicknesses. One problem with such a fastener is providing a structurein which the pin break will occur repeatedly and consistently in adesired one of the combination grooves.

This is accomplished by the present invention which utilizes a pinhaving a unique combination groove geometry. In addition, it is believedthat the use of a selective relative hardness between the pin andassociated tubular member further assists in the proper functioning ofthe fasteners. In the present invention, an axially directed forcegenerated by the swaging of the tubular member into a preselected one ofthe combination grooves is utilized at a preselected groove which forcewhen combined with a pulling force applied via a plurality of jaws by aninstallation tool will provide a combined tensile force at the selectedgroove whereby fracture will occur and hence that groove when selectedfunctions as a breakneck. The groove geometry includes a pair ofradially outwardly diverging sidewalls defining each groove, each ofwhich sidewall forms a different angle with respect to a radial planeextending transversely through the pin member and controlled radiusportions interconnecting adjacent end portions thereof.

Because of the unique contour of the combination grooves, conventionaljaw structures in the installation tool may in some cases have reducedlife and hence a modified jaw structure having teeth with a contour moreclosely matching that of the combination grooves may be desirable;however, in some cases it would be advantageous to be able to utilizetools with existing jaw structures. Thus in one form of the inventionthe end portion of the pin is provided with a plurality of pull grooveswhich are contoured differently from the combination grooves and whichare adapted for use with existing jaw structures.

Accordingly, the present invention provides an improved two piecefastener having combination locking and breakneck grooves which extendalong the shank portion of the pin a distance at least equal to thelength of the shank portion less the minimum material thickness forwhich such fastener is to be used. This invention thereby enables asingle fastener to be utilized to secured materials having a widevariety of total thicknesses. This feature affords substantial costsavings to users of such fasteners both by reducing the number ofdifferent fasteners required to be purchased and carried in theirinventory as well as increasing product reliability by reducing thelikelihood of a fastener with an inappropriate gripping range beinginadvertently used. In one form of the invention an end portion of thepin is provided with a plurality of pull grooves of a shape differentfrom that of the combinatin grooves with the pull grooves being adaptedfor use with existing jaw structures.

Additional advantages and features of the present invention will becomeapparent from the subsequent description and the appended claims takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially sectioned view of a fastener in accordance withthe present invention shown in operative relation to a pair ofworkpieces and having an installation tool in initial engagement withthe fastener;

FIG. 2 is an enlarged fragmentary sectioned view of a portion of thefastener pin of FIG. 1 illustrating the groove geometry of the presentinvention, the section being taken along an axial plane;

FIGS. 3, 4 and 5 are a sequence of views each similar to FIG. 1 butillustrating the installation sequence from initial swaging of thetubular member through completed swage and pin break;

FIG. 6 is a partially sectioned view of a modified form of fastener ofthe present invention shown with workpieces of a minimum combinedthickness and with a portion of an installation tool;

FIG. 7 is a partially sectioned view of the modified form of fastener ofFIG. 6 shown with workpieces of a maximum combined thickness and with aportion of an installation tool; and

FIG. 8 is an enlarged fragmentary, sectioned view of the portion of thefastener pin of FIG. 6 shown in the circle designated by the numeral 8and illustrating the groove geometry of pull grooves on the pin.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings and in particular to FIGS. 1 and 2thereof, there is illustrated a fastener indicated generally at 10 inaccordance with the present invention and comprising a pin member 12having a head 14 provided on one end thereof and an elongated shankportion 16.

Shank portion 16 has a plurality of substantially identical annularcombination locking and breakneck grooves 18 extending alongsubstantially the entire length thereof and may include a relativelyshort smooth cylindrical portion 19 immediately adjacent the juncturewith head 14. While smooth cylindrical portion 19 is illustrated asbeing relatively short, it may extent up to a length equal to apredetermined minimum total material thickness with which fastener 10 isto be used. Thus, grooves 18 will extend along the length of shank 16from a point greater than this predetermined minimum thickness. Each ofgrooves 18 is defined by radially outwardly diverging sidewalls 20 and22 which are connected at their radially inner ends by a generallyconcave radiused portion 24. The radially outer end of sidewall 20 isinterconnected with the radially outer end of sidewall 22 of the nextadjacent groove 18 by a generally convex radiused portion 26 and, inlike manner, a substantially identical convex radiused portion 26 alsoconnects the radially outer end of sidewall 22 with sidewall 20 of thenext adjacent groove 18.

As best seen with reference to FIG. 2, sidewall 20 is disposed at asubstantially smaller angle 28 relative to a radial plane 30 extendingtransversely through the shank portion 16 than the angle 32 formedbetween sidewall 22 and radial plane 30. It has been found that thepresent invention provides satisfactory results when angle 28 isapproximately 20° and angle 32 is approximately 45°.

Another important aspect of the present invention resides in theprovision of the convex radiused portions 26 and concave radiusedportions 24. It has been found that consistent results have beenachieved with pin members having a shank diameter of approximately 0.25inches when the concave radiused portions 24 have a radius no less thanaround 0.005 inches and are preferably in the range of from around 0.005to about 0.010 inches. It has also been found that consistent resultsare achieved with such pin members when the convex radiused portions 26have a radius less than around 0.010 inches. The selection of radii forportions 24 and 26 as noted promotes consistency in operation. As thepin diameter increases, the preferred range for concave radiused portion24 will also increase in a substantially linear relationship maintaininga ratio in the range of approximately 50:1 to 50:2. Similarly withrespect to the convex radiused portion, the allowable maximum radius mayalso increase in a substantially linear relationship to increasingdiameter such that the ratio of pin diameter to convex radius isapproximately a maximum of 50:2.

Referring now to FIGS. 1 and 3 through 5, it is seen that fastener 10 isdesigned to be inserted in aligned openings 34 and 36 provided in a pairof members 38 and 40, respectively, which are to be joined by fastener10. A tubular member 42 in the form of a generally cylindrically shapedcollar is placed on shank portion 16 with flanged end portion 44 thereofbeing brought into engagement with member 40. As shown, shank portion 16is of a length substantially greater than the total thickness of members38 and 40 plus the axial length of collar 42 thereby providing an endportion 46 also having combination grooves 18 which grooves may beengaged by jaws 48 of pulling tool 50.

Pulling tool 50 is of conventional construction having a swaging anvil52 extending outwardly from the nose portion 54 of the tool 50; the jaws48 are adapted to be moved rearwardly relative to anvil 52 as shown inthe drawings. Anvil 52 of pulling tool 50 has a central frusto conicallyshaped opening 58 provided therein having a first relatively sharplytapered inner portion 60 and second tapered inner portion 62. It hasbeen found that an anvil in which portion 60 is provided with a taper ofapproximately 31.5° relative to the axis thereof and extending inward adistance of about 0.090 inches and portion 62 is provided with a taperof approximately 7° relative to the axis thereof produces satisfactoryresults in setting fasteners of the present invention.

Actuation of pulling tool 50 will cause jaws 48 to engage and grip apredetermined number of combination grooves 18 and thereby exert apulling or tensioning force upon pin 12 and against collar 42. Duringthe initial stages of the pulling action, anvil 52 exerts an oppositelydirected force on collar 42 thereby causing members 38 and 40 to bedrawn into mutual engagement.

Thereafter, as best seen in FIG. 3, portion 60 of anvil 52 begins todeform or cause the outer end portion 56 of collar 42 to be extrudedinto a preselected one 18a of combination grooves 18. This initialdeformation causes a locking action to occur between collar 42 and pin12. Thereafter, continued movement of jaws 48 cause anvil 52 to movealong collar 42 thereby causing the collar material to flow intocombination grooves 18b, c, d, e and possibly others approaching members38 and 40 as well as continuing to compress the collar material whichhas been swaged into groove 18a.

Because of the defined groove configuration, the continued compressionand flow of the collar material into groove 18a causes an axiallydirected localized force to be exerted on sidewall 20 as a portion ofthe collar material experiences a backward extrusion or flowing to theright as seen in the drawings into the next outwardly disposed groove18f. The axial component of swaging or material flow force developed bythis continued compression and flow of the collar material incombination with the axial tension exerted by the pulling action of thejaws 48 will cause groove 18a to function as a breakneck with endportion 46 of pin 12 breaking thereat. As illustrated, groove 18a isdesirably the outermost groove which is first filled with collarmaterial.

As previously mentioned, concave radiused portion 24 is selected so asto provide an area of predetermined controlled stress concentrationwhich facilitates fracture thereby enabling the present invention torepeatedly control the desired groove at which portion 46 of shank 16separates. Also, radiused convex portion 26 operates to facilitate metalflow into groove 18a thereby assisting in providing control of theselection of the groove at which fracture occurs.

The relative hardness of collar 42 with respect to pin 12 has also beenfound to be a contributing factor in the operation of the presentinvention in producing a commercially acceptable joint. A collar havingtoo high a hardness relative to a given pin hardness will not providesufficient metal flow to enable the generation of axial forces frommetal flow within groove 18a. An excessively soft collar may operate toproduce satisfactory pin breaking action but the resulting joint maythen have insufficient strength to be commercially acceptable orpractical. It has been found that with pin members 12 fabricated fromsteel and having a hardness in the range of approximately 15R_(C) to25R_(C) a collar having a hardness in the range of approximately 45R_(B)to 65R_(B) produced satisfactory results.

It should be noted that in the present invention the tensile loadrequired to be applied by the installation tool to effect pin break ofthe fastener when installed in combination with the tubular member willbe lower than the tensile load required to effect pin break thereofwithout the cooperation of the tubular member.

In summary, the present invention comprises the concepts of theutilization of a pin having a plurality of similarly constructed grooveswhich function both as locking and breakneck grooves and in which thegroove shape including the desired radiused portions provides a meanswhereby any one of the grooves located at a selected location proximatethe outer end of the collar will function as a breakneck. In addition tothe above, a desired relative pin and collar hardness assists inproducing the desired result. This ability to consistently control thegroove at which fracture occurs enables a single fastener to bemanufactured which can accommodate a very broad range of materialthicknesses.

It should also be noted that while the present invention has beendescribed with reference to a two piece fastener having a pin andswageable collar, the principles are also applicable to fabrication of ablind fastener in which tubular member 42 may be in the form of acylindrical sleeve having an outer portion adapted to be swaged to a pinin a manner similar to that described above.

In some cases it may be desirable to utilize the present invention withinstallation tools having jaws of a conventional structure and in theembodiment as illustrated in FIGS. 6-8 an end portion 200 is provided tohave a plurality of pull grooves 202 which are contoured differentlythan the combination grooves 18 of FIGS. 1-5 and facilitate the use ofjaws of a conventional structure. For purposes of simplicity in theembodiment of FIGS. 6 and 7, elements and portions similar to likeelements and portions in the embodiment of FIGS. 1-5 and performingsimilar functions have been given the same numerical designationsincreased by `100's` i.e. workpieces 38 and 40 of FIGS. 1-5 become 138and 140, respectively in FIG. 6.

Thus fastener 110 has a pin member 112 which now has an end portion 200having a plurality of pull grooves 202 and an inner portion 204 havingthe combination locking and breakneck grooves 118 (similar to grooves 18of FIGS. 1-5). The pull grooves 202 can be of a conventional structuresuch as that generally shown in FIG. 8. Note that the pull grooves 202are more shallow than the combination grooves 118, i.e. crests 203 arenot as high as crests 126 and roots 205 are not as deep as roots 124. Atthe same time the engaging teeth of jaws 207 are shaped similarly topull grooves 202 resulting in a good match therebetween. The pullgrooves 202 will not provide the desirable locking and breakneckcharacteristics of combination grooves 116 and therefore it is importantthat the collar 142 not be swaged into the pull grooves 202; thus whilethe crests 126 of combination grooves 118 are shaped and/or contoured tofacilitate metal flow of the collar 142 and the roots 124 are shapedand/or contoured to provide a desired stress concentration, aspreviously described. The roots 205 of pull grooves 202 are shaped toavoid an effective stress concentration of the magnitude of that ofgrooves 118 and the crests 203 are not shaped to facilitate metal flow;thus pull grooves 202 can be designed to optimize the pulling functionand the effectiveness of jaws 207. FIG. 6 therefore illustrates thecondition of maximum grip, i.e. combined thickness, T max, forworkpieces 138 and 140.

At the same time, since jaws 148 are shaped similarly to pull grooves202 it is also important that the jaws 148 do not grip the pin member112 at the combination grooves 118. Thus FIG. 7, illustrates thecondition of minimum grip, i.e. combined thickness, T min, forworkpieces 238 and 240.

It can be seen from FIG. 7 that the length of inner portion 204 withcombination grooves 118, in order to accommodate the minimum gripcondition, T min, will be at least equal to the sum of the minimum grip(T min) plus the length (C.L.) of the collar 142, i.e. T min+C.L. Oncehaving determined the minimum grip, T min, the maximum grip (T max) willbe approximately equal to the minimum grip, T min, plus the distance (D)measured from the point of engagement of the anvil 152 with the collar142 to the forward face of the jaws 207. Now the length of inner portion204 with combination grooves 118 in order to accommodate the maximumgrip condition, T max, will be approximately equal to the sum of theminimum grip, T min, plus the length (C.L.) of collar 142 plus the anvilto jaw distance (D) i.e. T min+C.L.+D. Thus the grip range for thefastener 110 will be from T min to T max (and will be approximatelyequal to the distance D) and this grip range will be accommodated by onepin member 112 having an inner portion 204 with a length of (Tmin+C.L.+D). Note that in the application of the above formulations,accommodation will be made for the length of a transition portion 206located between the combination grooves 118 and pull grooves 202. Thelength of transition portion 206 will, of course, be maintained at aminimum.

Assuming a T min of 1/16" and a collar length (C.L.) of 3/8" and aninstallation tool 150 having a D dimension of 9/16", then with innerportion 204 having a length of T min+C.L.+D=1/16"+3/8"+9/16" thefastener 110 will have a grip range of D or 9/16" and will be able toaccommodate workpieces having a combined thickness in the range of from1/16" to 5/8", i.e. with the 5/8" being the sum of T min plus D or1/16"+9/16". A second pin member to accommodate workpieces of greatercombined thicknesses can be readily determined by providing T min equalto 5/8" and then having T max equal to 5/8"+9/16" (T min+D) or 1-3/16";in the latter situation the length of inner portion such as 204 would beT min+C.L.+D or 5/8"+3/8"+9/16" or 1-9/16". Note that the grip rangestill would be D or in the example given would be 9/16". The above areby way of examples and should be considered to be approximations.

In any case, where the total length of the pin 112 is to be minimized,the length of the end portion 200 could be a fixed dimension and wouldnot vary with the grip range and would be approximately equal to the sumof the D dimension plus the length JL of the jaws 207, i.e. D+JL.However, for a minimum length pin, in situations where pull together ofthe workpieces is contemplated then the length of end portion 200 shouldbe increased by between approximately one half to one times the nominaldiameter Dp of the pin member 112 and in that case the length of endportion 200 would be generally fixed at a dimension of D+JL+(between 1/2and 1)×Dp.

Thus with the construction of a fastener 110 having a pin member such as112 a single pin member can accommodate a wide grip range andconventional jaw structures can be utilized. For a given grip range, useof approximately the minimum length necessary for end portion 200 willresult in a reduction in the amount of material to be discarded afterthe fastener is set, i.e. the length of the pin member 112 from the onegroove 116 at which it severs to the end.

In the latter discussion, elements 114, 119, 134, 136, 144, 154, 156,158 and 162 of FIGS. 6-8 are similar to and perform functions similar totheir lower numbered counterparts, i.e. 14, 19, etc., of FIGS. 1-5 andhence a description of these elements has been omitted for purposes ofsimplicity.

While it will be apparent that the preferred embodiment of the inventiondisclosed is well calculated to provide the advantages and featuresabove stated, it will be appreciated that the invention is susceptibleto modification, variation and change without departing from the properscope or fair meaning of the subjoined claims.

What is claimed is:
 1. In a two piece fastener for fastening a pluralityof workpieces together with the workpieces having a thickness varyingfrom a determinable minimum to a determinable maximum thickness,comprising a pin member having a head and a shank portion having aplurality of grooves thereon and a tubular member adapted to be swagedinto locking engagement with a predetermined number of said grooves onthe shank portion of the pin member by means of a tool having a swaginganvil adapted to engage the tubular member and gripping means adapted togrip a gripping portion of the shank portion, the tool being actuable toapply a relative axial tensile force between the pin member and thetubular member whereby the tubular member is swaged into saidpredetermined number of said grooves on the shank portion of the pinmember, at least said predetermined number of said grooves being annularcombination locking and breakneck grooves, each of said predeterminednumber of said grooves being defined by first and second radiallyoutwardly diverging sidewalls, the improvement comprising the junctureof said diverging sidewalls at each of the grooves including a concaveradius portion interconnecting the radially inner ends of said first andsecond sidewalls, a selected one of the grooves being located at apredetermined location proximate the outer end of the tubular member andadapted to receive the material of the tubular member as it is swagedonto the shank portion, said first and second sidewalls being angulatedsuch as to provide a relative force between said sidewalls in saidselected one of the grooves, said force being generated by the materialof the tubular member as it is swaged therein, wherein said relativeforce will be additive with the relative axial tensile force applied bythe tool such that the shank portion will fracture at said selected oneof the grooves, said convace radius portion being of a magnitudeselected to provide a predetermined stress concentration to facilitatefracture at said selected one of the grooves in response to thecombination of said relative force and said relative axial tensileforce, any one of the grooves being capable of functioning as saidselected one of the grooves when located at said predetermined locationwhile said pulling tool exerts the relative axial tensile force on thepin member, said gripping portion of the shank portion located at theend opposite said head and having a plurality of different groovesadapted to be gripped by the gripping means of the tool, said differentgrooves having a shape different from that of said combination groovesto avoid an effective stress concentration of the magnitude of saidpredetermined stress concentration and wherein said different grooveshave an axial length substantially equal to the distance between thepoint of engagement of said swaging anvil with said tubular member andthe forward end of said gripping means plus the axial length of theportion of said gripping means engaging said gripping portion less theaxial length of the transition portion.
 2. The fastener of claim 1 withsaid combination grooves providing a preselected grip range from thedeterminable minimum to the determinable maximum such that the tubularmember will be swaged substantially only into said combination groovesfor workpieces within said grip range and the gripping means willsubstantially engage only said different grooves for workpieces withinsaid grip range.
 3. In a two piece fastener for fastening a plurality ofworkpieces together with the workpieces having a thickness varying froma determinable minimum to a determinable maximum thickness, comprising apin member having a head and a shank portion having a plurality ofgrooves thereon and a tubular member adapted to be swaged into lockingengagement with a predetermined number of said grooves on the shankportion of the pin member by means of a tool having a swaging anviladapted to engage the tubular member and gripping means adapted to gripa gripping portion of the shank portion, the tool being actuable toapply a relative axial tensile force between the pin member and thetubular member whereby the tubular member is swaged into saidpredetermined number of said grooves on the shank portion of the pinmember, at least said predetermined number of said grooves beingsimilarly contoured annular combination locking and breakneck grooves,each of said predetermined number of said grooves being defined by firstand second radially outwardly diverging sidewalls, said first sidewallbeing positioned closer to said head then said second sidewall andforming an included angle with a radial plane extending transverselythrough said shank greater than the angle formed by said secondsidewall, the improvement comprising the juncture of said divergingsidewalls at each of the grooves being defined by a concave radiusportion interconnecting the radially inner ends of said first and secondsidewalls, a selected one of the grooves being located at apredetermined location proximate the outer end of the tubular member andadapted to receive the material of the tubular member as it is swagedonto the shank portion, said first and second sidewalls being angulatedsuch as to provide a relative axial force between said sidewalls in saidselected one of the grooves, said force being generated by the materialof the tubular member as it is swaged therein, whereby said relativeaxial force will be additive with the relative axial tensile forceapplied by the tool such that the shank portion will fracture at saidselected one of the grooves, said concave radius portion being of amagnitude selected to provide a predetermined stress concentration tofacilitate fracture at said selected one of the grooves in response tothe combination of said relative axial force and said relative axialtensile force, any one of the grooves being capable of functioning assaid selected one of the grooves when located at said predeterminedlocation while said pulling tool exerts the relative axial tensile forceon the pin member, said gripping portion of the shank portion located atthe end opposite said head and having a plurality of different groovesadapted to be gripped by the gripping means of the tool, said differentgrooves having a shape different from that of said combination groovesto avoid an effective stress concentration of the magnitude of saidpredetermined stress concentration, said combination grooves providing apreselected grip range from the determinable minimum to the determinablemaximum such that the tubular member will be swaged substantially onlyinto said combination grooves for workpieces within said grip range andthe gripping means will substantially engage only said different groovesfor workpieces within said grip range, said grip range being the maximumallowable for the full operation of the swaging anvil and gripping meansof the tool.
 4. The fastener of claim 3 with the gripping means of thetool comprising a plurality of jaws and with said maximum allowable griprange being selected to be approximately the distance from the point ofengagement of the swaging anvil with the tubular member to the beginningof said jaws.
 5. The fastener of claim 4 with said different groovesextending for a length approximately equal to the sum of said maximumallowable grip range plus the effective length of the jaws.
 6. Thefastener of claim 4 with said different grooves extending for a lengthapproximately equal to the sum of said maximum allowable grip range plusthe effective length of the jaws plus a length equal to approximately nomore than the diameter of the shank portion.
 7. The fastener of claim 4with said combination grooves extending along said shank portion from apoint equal to at least around the minimum thickness to a pointapproximately equal to the length of the tubular member extending beyondthe workpieces plus the distance from the point of engagement of theswaging anvil with the tubular member to the beginning of said jaws. 8.The fastener of claim 7 with said different grooves extending for alength approximately equal to the sum of said maximum allowable griprange plus the effective length of the jaws plus a length equal toapproximately no more than the diameter of the shank portion.
 9. Thefastener of claim 6 wherein the tubular member has a preselectedhardness less than the pin member and related thereto such that saidtubular member has a hardness in the range of approximately from 45R_(B)to 65R_(B) when said pin has a hardness in the range of approximatelyfrom 15R_(C) to 25R_(C) so as to thereby provide controlled flow of theswaged material of the tubular member whereby fracture will occur atsaid selected one of the grooves.
 10. In a two piece fastener forfastening a plurality of workpieces together with the workpieces havinga thickness varying from a determinable minimum to a determinablemaximum thickness, comprising a pin member having a head and a shankportion having a plurality of grooves thereon and a tubular memberadapted to be swaged into locking engagement with a predetermined numberof said grooves on the shank portion of the pin member by means of atool having a swaging anvil adapted to engage the tubular member andgripping means adapted to grip a gripping portion of the shank portion,the tool being actuable to apply a relative axial tensile force betweenthe pin member and the tubular member whereby the tubular member isswaged into said predetermined number of said grooves on the shankportion of the pin member, at least said predetermined number of saidgrooves being substantially identical annular combination locking andbreakneck grooves, each of said predetermined number of said groovesbeing defined by first and second radially outwardly divergingsidewalls, said first sidewall being positioned closer to said head thansaid second sidewall and forming an included angle with a radial planeextending transversely through said shank greater than the angle formedby said second sidewall, the improvement comprising the juncture of saiddiverging sidewalls at each of the grooves being defined by a concaveradius portion interconnecting the radially inner ends of said first andsecond sidewalls, a selected one of the grooves being located at apredetermined location proximate the outer end of the tubular member andadapted to receive the material of the tubular member as it is swagedonto the shank portion, said first and second sidewalls being angulatedsuch as to provide a relative axial force between said sidewalls in saidselected one of the grooves, said force being generated by the materialof the tubular member as it is swaged therein, whereby said relativeaxial force will be additive with the relative axial tensile forceapplied by the tool such that the shank portion will fracture at saidselected one of the grooves, said concave radius portion being of amagnitude selected to provide a predetermined stress concentration tofacilitate fracture at said selected one of the grooves in response tothe combination of said relative axial force and said relative axialtensile force, said concave radius portion having a radius related tothe pin diameter in a range of between the ratio of around 1:50 andaround 2:50 so as to provide said predetermined stress concentration,any one of the grooves being capable of functioning as said selected oneof the grooves when located at said predetermined location while saidpulling tool exerts the relative axial tensile force on the pin member,said gripping portion of the shank portion located at the end oppositesaid head and having a plurality of different grooves adapted to begripped by the gripping means of the tool, said different grooves havinga shape different from that of said combination grooves to avoid aneffective stress concentration of the magnitude of said predeterminedstress concentration, said combination grooves providing a preselectedgrip range from the determinable minimum to the determinable maximumsuch that the tubular member will be swaged substantially only into saidcombination grooves for workpieces within said grip range and thegripping means will substantially engage only said different grooves forworkpieces within said grip range, said grip range being the maximumallowable for the full operation of the swaging anvil and gripping meansof the tool.
 11. The fastener of claim 10 with the gripping means of thetool comprising a plurality of jaws and with said maximum allowable griprange being selected to be approximately the distance from the point ofengagement of the swaging anvil with the tubular member to the beginningof said jaws, said different grooves extending for a lengthapproximately equal to the sum of said maximum allowable grip range plusthe effective length of the jaws, said different grooves extending for alength approximately equal to the sum of said maximum allowable griprange plus the effective length of the jaws plus a length equal toapproximately no more than the diameter of the shank portion.
 12. Thefastener of claim 11 with said combination grooves extending along saidshank portion from a point equal to at least around the minimumthickness to a point approximately equal to the length of the tubularmember extending beyond the workpieces plus the distance from the pointof engagement of the swaging anvil with the tubular member to thebeginning of said jaws.
 13. The fastener of claim 12 wherein the tubularmember has a preselected hardness less than the pin member and relatedthereto such that said tubular member has a hardness in the range ofapproximately from 45R_(B) to 65R_(B) when said pin has a hardness inthe range of approximately from 15R_(C) to 25R_(C) so as to therebyprovide controlled flow of the swaged material of the tubular memberwhereby fracture will occur at said selected one of the grooves.
 14. Ina two piece fastener for fastening a plurality of workpieces togetherwith the workpieces having a thickness varying from a determinableminimum to a determinable maximum thickness, comprising a pin memberhaving a head and a shank portion having a plurality of grooves thereonand a tubular member adapted to be swaged into locking engagement ontothe shank portion of the pin member by means of a tool having a swaginganvil adapted to engage the tubular member and gripping means adapted togrip a gripping portion of the shank portion, the tool being actuable toapply a relative axial tensile force between the pin member and thetubular member whereby the tubular member is swaged into a predeterminednumber of said plurality of grooves of the shank portion of the pinmember, said predetermined number of said grooves being annularcombination locking and breakneck grooves, each of said predeterminednumber of said grooves being defined by first and second radiallyoutwardly diverging sidewalls, said first sidewall being positionedcloser to said head than said second sidewall and forming an includedangle with a radial plane extending transversely through said shankgreater than the angle formed by said second sidewall, the improvementcomprising the juncture of said diverging sidewalls at each of thegrooves being defined by a concave radius portion interconnecting theradially inner ends of said first and second sidewalls, a convex radiusportion interconnecting a said second sidewall of one of the grooves anda said first sidewall of an immediately adjacent one of the grooves, aselected one of the grooves being located at a predetermined locationproximate the outer end of the tubular member and adapted to receive thematerial of the tubular member as it is swaged onto the shank portion,said first and second sidewalls being angulated such as to provide arelative axial force between said sidewalls in said selected one of thegrooves, said force being generated by the material of the tubularmember as it is swaged therein, whereby said relative axial force willbe additive with the relative axial tensile force applied by the toolsuch that the shank portion will fracture at said selected one of thegrooves, said concave radius portion being of a magnitude selected toprovide a predetermined stress concentration to facilitate fracture atsaid selected one of the grooves in response to the combination of saidrelative axial force and said relative axial tensile force, said convexradius portion being of a magnitude selected to facilitate a desiredflow of material during swaging of the tubular member, any one of thegrooves being capable of functioning as said selected one of the grooveswhen located at said predetermined location while said pulling toolexerts the relative axial tensile force on the pin member, said grippingportion of the shank portion located at the end opposite said head andhaving a plurality of different grooves adapted to be gripped by thegripping means of the tool, said different grooves having a shapedifferent from that of said combination grooves to avoid an effectivestress concentration of the magnitude of said predetermined stressconcentration, said combination grooves providing a preselected griprange from the determinable minimum to the determinable maximum suchthat the tubular member will be swaged substantially only into saidcombination grooves for workpieces within said grip range and thegripping means will substantially engage only said different grooves forworkpieces within said grip range, said grip range being the maximumallowable for the full operation of the swaging anvil and gripping meansof the tool.
 15. The fastener of claim 14 with the gripping means of thetool comprising a plurality of jaws and with said maximum allowable griprange being selected to be approximately the distance from the point ofengagement of the swaging anvil with the tubular member to the beginningof said jaws, said different grooves extending for a lengthapproximately equal to the sum of said maximum allowable grip range plusthe effective length of the jaws on point plus a length equal toapproximately no more than the diameter of the shank portion, saidcombination grooves extending along said shank portion from a pointequal to at least around the minimum thickness to a point approximatelyequal to the length of the tubular member extending beyond theworkpieces plus the distance from the point of engagement of the swaginganvil with the tubular member to the beginning of said jaws.
 16. Thefastener of claim 15 wherein the tubular member has a preselectedhardness less than the pin member and related thereto such that saidtubular member has a hardness in the range of approximately from 45R_(B)to 65R_(B) when said pin has a hardness in the range of approximatelyfrom 15R_(C) to 25R_(C) so as to thereby provide controlled flow of theswaged material of the tubular member whereby fracture will occur atsaid selected one of the grooves.
 17. The fastener of claim 3 whereinsaid determinable minimum grip is approximately equal to saiddeterminable maximum grip plus the axial length of the transitionportion between said combination grooves and said different grooves lessthe axial distance between the point of engagement of said swaging anvilwith said tubular member and the forward face of that portion of saidgripping means engageable with said different grooves.
 18. In a twopiece fastener for fastening a plurality of workpieces together with theworkpieces having a thickness varying from a determinable minimum to adeterminable maximum thickness, comprising a pin member having a headand a shank portion having a plurality of grooves thereon and a tubularmember adapted to be swaged into locking engagement with a predeterminednumber of the grooves on the shank portion of the pin member by means ofa single action tool having a swaging anvil adapted to engage thetubular member and gripping means adapted to grip a gripping portion ofthe shank portion, the gripping means including a plurality of jawmembers having a plurality of teeth with a preselected pitch, the toolbeing actuable to set said fastener by applying a relative axial tensileforce between the pin member and the tubular member substantiallyentirely through said engagement of said swaging anvil with said tubularmember whereby the tubular member is swaged into the predeterminednumber of the grooves on the shank portion of the pin member, theimprovement comprising said pin member with at least said predeterminednumber of said combination grooves being annular combination locking andbreakneck grooves, each of said predetermined number of said combinationgrooves being defined by first and second radially outwardly divergingsidewalls, said first sidewall being positioned closer to said head thansaid second sidewall and forming a preselected included angle with aradial plane extending transversely through said shank, a selected oneof said combination grooves being located at a predetermined locationproximate the outer end of the tubular member and adapted to receive thematerial of the tubular member as it is swaged onto the shank portion bysaid swaging anvil whereby the shank portion will fracture at saidselected one of the grooves, any one of said combination grooves beingcapable of functioning as said selected one of said combination grooveswhen located at said predetermined location while said pulling toolexerts the relative axial tensile force on said pin member, saidgripping portion of the shank portion located at the end opposite saidhead and having a plurality of different grooves with a minimum lengthtransition portion between said combination grooves and said differentgrooves, said different grooves being adapted to be gripped by thegripping means of the tool, said different grooves having a shapedifferent from that of said combination grooves whereby said differentgrooves will not effectively function as a breakneck groove.